See Also
The OPF Dialog, Constraint Options page displays options associated with the enforcement of the constraints by the OPF. The display contains the following fields:
Line/Transformer Constraints
Disable Line/Transformer MVA Limit Enforcement
Select to disable enforcement of Line/Transformer MVA constraints for the entire case.
Percent Correction Tolerance
Specifies a tolerance for the enforcement of line/transformer MVA flows. The tolerance is necessary to prevent solution oscillations due to the non-linear nature of the actual constraints.
Violated elements are always enforced to their limits multiplied by the MVA Enforcement Percentage. If power systems were completely linear then following the LP solution the constraint would actually be equal to this value. However because of nonlinearities, the constraint is close to this value but usually not identical to the value. The Percent Correction Tolerance is used to tell the OPF how close is close enough. Provided all the constraints are violating their limits by less than the correction tolerance percentage the optimal solution is assumed to have been found. You may set this value as low as you like, but setting it too close to zero may result in convergence difficulties. The default is 2 percent.
MVA Auto Release Percentage
Specifies a MVA level at which transmission lines can be released as an OPF constraint equation if the branch MVA flow falls below the level specified.
Maximum Violation Cost ($/MWhr)
If a branch MVA limit cannot be enforced during an OPF solution, the branch will be assigned a fictitious cost of enforcement equal to this value. This value is usually rather large in order to easily determine where the unenforceable constraint is occurring. The default value is 1000 $/MWhr.
Enforce Line/Transformer MW Flow Limits (Not MVA)
Checking this box will cause Simulator to treat the limits of the transmission elements as MW limits instead of MVA limits. Thus Simulator will report violations on these elements in the OPF based on the MW flow of the element versus the element’s MVA rating.
Interface Constraints
Disable Interface MW Limit Enforcement
Select to disable enforcement of Interface MW constraints for the entire case.
Percent Correction Tolerance, MW Auto Release Percentage, Maximum Violation Cost ($/MWhr)
These fields are equivalent to the entries described above for Line/Transformer MVA Constraints except that they apply to Interface MW constraints.
Phase Shifting Transformer Regulation Limits
Disable Phase Shifter Regulation Limit Enforcement
Select to disable enforcement of Phase Shifter regulation limit constraints for the entire case.
For a phase shifter, there are two limits which can be enforced during the OPF—the MVA branch rating, and the regulation minimum and maximum MW flow. Checking this option will globally disable the enforcement of the regulation minimum and maximum MW flow for all phase shifters.
In Range Cost ($/degreehr)
The cost of changing a phase shifter angle away from zero degrees in $/degreehr, when the angle is within the allowable range of the phase shifter.
Maximum Violation Cost ($/MWhr)
If a phase shifter regulation limit cannot be enforced during an OPF solution, it will be assigned a fictitious cost of enforcement equal to this value. This value is usually rather large in order to easily determine where the unenforceable constraint is occurring. The default value is 1000 $/MWhr.
Bus Constraints
Disable Bus Angle Enforcement
Select to disable enforcement of Bus Angle limit constraints for the entire case.
Maximum Violation Cost ($/deg-h)
This field is equivalent to the entries described above for Line/Transformer MVA Constraints except that they apply to Bus Angle constraint. The default value is 1000 $/deg-h.
D-FACTS Constraints
Please contact PowerWorld for more information about these options.
Limit Monitoring Settings…
This button opens the Limit Monitoring Settings dialog, which allows you to change the enforcement percentages for monitored elements.
Monitor/Enforce Contingent Interface Elements
This option cannot actually be set from this dialog, but it is important when including interfaces in the OPF solution. This option can be set on the Simulator Options dialog on the Power Flow Solution page under the General tab.
This option allows you to specify how contingency elements in an interface should be treated in Simulator. You can choose to never include the impact of contingent elements on interface flow, to only include contingent element impacts in the standard power flow or optimal power flow routines, or in all solution routines including contingency analysis and security constrained OPF.
It is not uncommon to ignore the impact of contingent elements when using the contingency analysis or security constrained OPF tools, as they are already processing lists of contingencies and evaluating flows on interfaces. Ignoring contingent elements within interface definitions allows for a determination of the impact of other contingencies on the flows of the non-contingent elements forming the interface, without impact from additional contingent element considerations.